It is frequently necessary to connect a motor or engine with a variety of different loads, for instance, pumps, and to have to change out the motor or the load at some time, often with one of a different design or manufacturer. Thus it is necessary to mount the relatively massive load so that its input shaft is as perfectly as possible aligned with the motor or engine's output shaft, typically formed by a flywheel.
The standard system is to provide a relatively massive cast or machined plate that on the one side fits with and can be bolted to the output side of the flywheel housing and on the other side fits with and can be bolted to the flange surrounding the input shaft of the load. Such a part is quite expensive to manufacture and must be designed for a specific type or style of motor or load, making it practically a custom item. When made of cast steel, as is common, it has a thickness of 12 mm to 16 and must be meticulously machined. Such an arrangement is shown in EP 0,515,929 of Hertell and German 4,134,369 of Maier.
Even though it is standard to make the loads with a standardized input side, typically a flange having bolt holes at a predetermined spacing flanking a central collar of predetermined diameter surrounding the input shaft, it is necessary to provide a special adapter for each standardized type. Some pump flanges have two bolt holes, and some have four, so that when a multiply drilled adapter is provided to accommodated both types, the result is open passages through the adapter that must be plugged when not used.